Keyboard switch assembly with ball and slider interlock mechanism

ABSTRACT

A keyboard has keys each of which when depressed displaces a row of balls and a column of balls respectively for operating two switches. The columns are associated with slides, and each slide is shifted when a key of the respective column is depressed, thereby blocking actuation of the other keys on that column. A slide when shifted projects into an additional row of balls and locks them so that none of the other slides can project into that additional row of balls, and all keys of the other columns are blocked for being depressed.

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KEYBOARD SWITCH ASSEMBLY WITH BALL AND SLIDER INTERLOCK MECHANISM BACKGROUND OF THE INVENTION The present invention relates to a keyboard with mechanically operating input encoding, and more particularly the invention relates to a keying arrangement with keys for actuating sets of contact springs of an encoding structure and in different combinations, whereby two sets of intersecting, displaceable control means are interposed between the switches and the control spring means for actuation thereby. The invention will find particular utility in telephone systems using code keying e.g. touch tone.

Selective keying arrangements of the type referred to above are known generally. They are, for example, constructed in that two sets of control rods, levers, slides or the like are disposed in two different planes, but they intersect when geometrically projected into a common plane. German Pat. No. 1,254,697, for example, discloses rods which are disposed in a first plane, and each rod can be turned. These rods constitute one of the sets of control means; the other set is established by angle rails disposed in a second plane underneath the first plane and these rails extend transversely to the rods of the first set. Each angle rail can be pivoted on one of its longitudinal edges.

The rods are provided with stops for being acted upon by the keys, and the rods carry cams for selective engagement in indentations in the angle rails. Thus, upon depressing a key one of the rods is engaged and turns in that its cams act on several angle rails which in turn operate switch blades or the like.

The known keying systems of that type are rather complicated, and they are particularly difficult to assemble. Moreover, assembly is followed by a rather tedious adjusting procedure of the several parts. Therefore, these particularly known key operated mechanical encoding systems are rather expensive.

Another type of keyboard-like mechanical encoding is disclosed in US. Pat. No. 3,470,332. The keyboard matrix is, so to speak, superimposed upon a matrix defined by rows and columns of balls. Upon depressing a key the balls of the particular intersecting row and column are displaced and actuate two switches, one being at the end of the row, the other one at the end of the column. The balls as so arranged are supposed to act also as locks, but only those keys which are arranged on that one row and those on that one column will in fact be locked. The remaining keys can still be depressed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a mechanically encoding keyboard which is simple to make and which is constructed to permit positive locking of all remaining keys once a key has been depressed.

It is a further object of the invention to improve on keyboards with mechanical encoding wherein the keyboard matrix is associated with a matrix of intersecting rows and columns of displaceable elements in that a key of the board is associated with an intersection of a row and of a column of those displaceable elements so that upon depressing the key these elements are displaced for actuating two switches, one at the end of the row the other at the end of the column.

In accordance with the preferred embodiment of the invention, it is suggested to provide an additional row of displaceable elements along side one of said rows but not pertaining to the matrix as established by the keyboard. A plurality of slide means is provided and respectively associated with the columns, one slide means per column, and each is displaced upon depressing of any one key of the respective column to engage, displace and lock the elements of the additional column, so that the other slide means cannot be displaced, and no longer will it be possible to displace the keys on the other columns because successfully depressing a key depends on displaceability of the slide means associated with the column to which the key pertains. Additionally, each slide means is constructed so that upon displacement by depression of one key, the other keys of the same column cannot be depressed.

The invention will find particular utility in telephone keyboards, and here it has to be observed that the triggered signals must have a minimum duration e.g. 40 milliseconds. Rapid manual keying may not always sustain key depressing for such a long" period of time. Therefore, it is suggested, additionally, to lock a displaced slide means for that period so that key depression and further actuation is maintained even if the key is released by the operator until the slide means is released and can return thereby causing the key to return (up) if the key was in fact already released by the operator.

DESCRIPTION OF THE DRAWINGS While the specification concludes with claims particularly pointing out and distinctly claiming the subject matter which is regarded as the invention, it is believed that the invention, the objects and features of the invention and further objects, features and advantages thereof will be better understood from the following description taken in connection with the accompanying drawings in which:

FIG. I is a sectional view through a keyboard improved in accordance with the preferred embodiment of the invention, the section is taken along a column of displaceable elements;

FIG. 2 is a top view of the keyboard, with phantom lines indicating rows and columns underneath thereby illustrating the superimposed matrices; and

FIG. 3 is a section view taken along lines 3-3 in FIG. 2, the section plane can be considered parallel to but viewed in the opposite direction'of the section plane of FIG. 1.

Proceeding now to the detailed description of the drawings, the keyboard illustrated herein has a base 1 composed of an upper part 2 and a lower part 3. The base parts are injection molded or the like, using a suitable plastic material. The lower part 3 includes e.g. partitions to define an array of channels of which channels 4 run in one direction and channels 5 run in the transverse direction. The channels are open at one end in each instance. The respective intersections of channels 4 and 5 can be understood to define the places or points of a matrix, and the keys or the keyboard are to be associated with these matrix points.

The channels are filled with balls 6 made for example of steel; such steel balls are readily available commercially. The balls filling the channels are displaceable elements arranged in rows and columns, whereby (arbitrarily) channels 5 define the rows and channels 4 de fine the columns.

A spring contact set 7 is disposed at the respective open end of each channel, engaging the respective closest ball 6 in the channel but being open under normal conditions. These sets of contacts define switches operated for translating the mechanical encoding into electrical encoding in that each switch closing affects an electric circuit, for example, for transmitting a signal or the like.

Upper part 2 as well as lower part 3 of the base or casing l is provided with openings which register in pairs and are traversed by stems 8 of keyboard keys 9. Each key is affixed to and receives the upper end of the respective stem 8. An annular slot in each key 9 receives additionally a spring 10 which bears with its lower end against the bottom of a groove in the top plate of upper part 2 and respectively circumscribes the opening as traversed by the respective key stem 8.

Each stem 8 carries a pair of blades, 11 and 12, respectively and oriented at right angles to each other. The blades are about as thick (or a little thicker) than the contact path to be traversed by the movable contact for each set and needed to close the contacts. As can be seen best from FIG. 2 the stem of a key is not directly above the respectively associated matrix point as defined by an intersection of a channel 4 with a channel 5 but is displaced down and to the right therefrom. The two blades 11 and 12 respectively extend into these two channels (i.e. 12 to 4 and 11 into 5) but only when the key is being depressed. Otherwise the blades hover about the balls in the respective channels. The partitions or dividers in casing l establishing the channels have slots into which the blades ll, 12 may drop when a key is depressed so that the respective blade can enter the channel from the outside even though the supporting stem is outside of the channels.

Upon depressing a key, the two blades 11, 12 wedge themselves between respective two balls in the respective channels. The balls are dimensioned so that all those between a blade and the closed end of a channel are not, or only very little, displaced. However, the balls between the respective blade and the open end of a channel are displaced and shifted towards the respective spring contacts of the respective set at this end of the channel. This action occurs twice per key, once at the end of a channel 4 and also at the end of a channel 5 so that these contact sets close.

Each contact set may be associated with a source of a unique frequency, and upon closing of the respective contacts that frequency is being transmitted. Hence, two frequencies issue upon depressing a key, and the two frequencies together uniquely identify the key (or vice versa). This way, the keyboard can be used, for example, in a touch tone system for telephone communication. Generally speaking, the two frequencies constitute a code that is being transmitted in representation of actuation of a particular key.

Each key stem 8 carries additionally a laterally protruding pin 13. These pins do not protrude into any of the channels but in the square space between two pairs of the othogonal channels. The pins 13 of all keys and key stems arranged along a channel 4 (and establishing for example a column of the matrix), all are disposed above a slide 15, there is one slider per column accordingly.

As can be seen best from FIG. 3 each such pin (for a non-depressed key) 13 is disposed above the entrance of an oblique slot 14 in the respective slide 15. The slots 14 function as cam surface in that the slide is longitudinally displaced upon depressing any one key of the respective column; the slide displacement occurs, in FIG. 3, to the right. Conversely, the slide will return to the left when a key is being lifted. However, if a slide is being moved to the left, a depressed key will be lifted up therewith.

Each slide is actually constructed as an elongated flate bar which extends underneath the bottom of lower casing portion 3. The flat bars has lugs which extend through elongated slots in the bottom of part 3, and these lugs have the cam slots 14. The slide, therefore, can slide to the extent the slots in the bottom of part 3 permit any displacement, and this displacement can be made under control of each of the keys through cam operation between the respective pin 13 and the respective slot 14 underneath.

EAch slide 15 is biased by a spring, tending to pull the slide 15 to the left, in which position the entrances to cam slots 14 are indeed underneath the respective pin 13. Upon depressing a key the slide is displaced against the force of the spring 16. Upon mere release of the depressed key the slide will be returned by the spring, and the respective cam slot 14 lifts the key stem up by guiding the pin 13 in the up direction.

The other end of a slide 15 has a nose 17 for cooperation with a ball lock, constructed as follows. An additional channel or duct 19 is provided in base 1, running in parallel to (row) channels 5 and adjacent one of them as can be seen in the top part of F lG. 2. The channel 19 is closed at both ends and filled with balls leaving just enough clearance that a nose 17 can pass in between two balls, but not the two noses of two different slides. A nose 17 will dip into channel 19 only when one of the keys along the particular slide (pertaining to the same matrix column) is depressed and has displaced the slide.

The arrangement as comprised of the ball lock 18, 19 and of the plural slides 15 permits actuation of but a single key at a time. Upon depressing a key, the respective slide is advanced, so that the nose l7 enters channel 19, and the now wedged-in balls in that channel will not permit the nose of another slide to enter. On the other hand, the displacement of a slide by operation of a key causes the entrances of all other slots of the same slide to be displaced. Accordingly, the other keys of the same column cannot be displaced as their respective pins 13, if attempted to be depressed, will hit the upper edge of the respective lug. Thus, only one key at a time can be depressed indeed. All other keys are locked and cannot be depressed, either becasue the respective pins 13 are stopped or the slides cannot move. This locking feature is important for observing a particular code format such as two frequencies per transmission. The locking device is, therefore, beneficial for telephone systems for preventing improper dialing.

FIG. 2 readily illustrates further versatility. The super-positioning of the keyboard matrix or array and of the channel matrix or array is convenient under the circumstances. However, each key may be located in the center of the square as defined by two adjacent row-channels and two adjacent column channels. Blades may be provided to displace the balls in both rows and in both columns, but not necessarily so; the

actuator may be different from key to key if the situation so requires.

Consider some further aspects of telephone systems which, however, may be of general significance; it may be necessary, for example, to have each contact set closed for a minimum period of time to ensure proper signalling. Thus, a key once depressed should remain depressed for at least that period of time.

ln order to eliminate human error as far as metering this minimum period of time is concerned, a locking pawl 21 is provided and associated with all slides 15. Each slide has a detent 22, but pawl 21 drops into the detent of that slide and looks it, only upon displacement of a slide. If the depressed key is released too early, the slide is held in the locking position so that the key will not be moved up again by cam slot action. Accordingly, the two sets of contacts remain actuated.

Pawl 21 is under control of an electro magnet 23 which is energized or responds a predetermined period after actuation of any key. Pawl 21 may actually be the armature of that magnet. Upon energizing the magnet 23, pawl 21 retracts, and the respective spring 16 now retracts the slide; the slot 14 guides the released key up. The blades 11 and 12 on the respective key stem 8 are taken up, and the contact springs of sets 7 push the balls of the two channels (one of 4, one of 5) back. The duration of contact actuation is rendered independent from the duration of key depressing as far as shortness of the latter action is concerned, because release of the respective slide by the electro magnet is needed.

The magnet may be under control of a switch which can be actuated by each of the slides when displaced by key actuation. The inductance of the magnet may be selected to be relatively large so that the magnet has a particular response delay. That delay should be equal to the minimum period of time of maintaining a key depressed.

The invention has been explained by way of example, but modifications of that example are quite conceivable. ln lieu of balls 6 one could use cylindrical rolls or cubes with bevelled edges. Moreover, not all these types of displaceable elements have to be of the samd size. It is important, however, that a displaceable element is directly in each intersection when no key is depressed and that element must be capable of displacement into one or the other of the two channels intersecting at that point.

ln lieu of channels defined by partitions one can use other means for guiding the displaceable bodies along linear walls, such as grooves, rails etc. and these channels do not have to intersect at right angles, though one could still term them rows and columns. The invention was explained on the basis of a two dimensional actuator matrix. However, one could stack several levels of such matrices of displaceable elements so that more than two switches are actuated by each key. The stems 8 may reach into all different levels. It is, of course, not necessary to have switches at the one end each of all rows and columns in all the different levels so that less than the maximum number of signals are presented in certain cases. A similar or analogous but functionally different result with a higher degree of versatility can be obtained if switches are provided at the end of each row and of each column, but the key stems do not have to have actuator blades for each respectively adajcent row and column. This way, one can obtain a more selective omission of signal actuation. However, it is important to note, that the locking against multiple key actuation is independently from this selectivity, because the locking does not depend on the displacement of the switch operating bodies (balls, etc.).

The invention is not limited to the embodiments described above but all changes and modifications thereof not constituting departures from the spirit and scope of the invention are intended to be included.

I claim:

1. In a keyboard having a plurality of keys arranged in a matrix and wherein a plurality of individual displaceable elements are arranged in intersecting rows and columns for displacement along the rows and columns upon actuation of individual ones of the keys, the keys being arranged in positions corresponding to the intersections of the rows and columns of displaceablc elements so that upon displacement of a key the elements in the respective row and the elements in the respective column intersecting in the intersection associated with the key are being displaced, there being switching means associated with the rows and columns of elements and actuated upon displacement of the elements in the respective rows and columns, the improvement comprising:

an additional row of displaceable elements arranged alongside one said rows and arranged for limited displacement only of the elements of the additional row; and plural slide means, respectively associated with said columns and operatively coupled to the keys so that one slide means of the plurality is displaced upon depression of a key pertaining to the column with which the one slide means is associated,

each slide means when displaced locking the elements of the additional row, so that the elements of the additional row inhibit displacement of the remaining slide means of the plurality thereby inhibiting depression of any key of the respective other columns.

2. ln a keyboard as in claim 1, wherein each slide means is constructed for operating, upon displacement, as stop for the keys of said column other than the one that has been depressed.

3. In a keyboard as in claim 1, wherein each key is provided with means for selective engagement with the respective slide means when undisplaced, for displacement of the slide means upon further depressing of the key, the key remaining in engagement with the slide means and remaining depressed for as long as the slide means remains displaced, there being spring means to return the slide means upon release of the ley, whereupon the key is raised by engagement with the returning slide means.

4. In a keyboard as in claim 3, and including timed locking means actuated upon depressing any of the keys and holding the respective displaced slide means in displaced position for a predetermined period of time, independently from the release of the key.

5. In a keyboard as in claim 4, the timed locking means including a pawl locking any displaced slide means, and a timer for retracting the pawl for unlocking the slide means a predetermined period after depressing of the key.

6. In a keyboard as in claim ll, including a first plurality of channels holding displaceable elements and a second plurality of channels holding displaceable elements and intersecting the channels of the first plurality, the

elements in the channels of the first plurality defining the rows of elements, the elements in the channels of the second plurality defining the columns, the keys disposed above the channels, each key having a stem projecting down, next to, but not into the respective intersection to which the key pertains, the stem having first and second blades respectively placeable into the intersecting channels, the slide means of the plurality each including a slide with oblique cam slots, the stems of the key of the column to which the slide means pertains having pins insertable into the cam slots upon depression of a key and when the slide is not displaced.

7. in a keyboard as in claim 1, wherein said slide means include a slide with a plurality of slots having oblique orientation to both, a direction of sliding displacement of the slide means and to directions of displacement of the keys on the respective column, each key on the column having a pin for entering a slot of the plurality upon depression of a key thereby sliding the slide in the said direction; and spring means for retracting the slide when a depressed key is released, whereby the respective slot guides the pin to return in up direction.

the released key following that up return. 

1. In a keyboard having a plurality of keys arranged in a matrix and wherein a plurality of individual displaceable elements are arranged in intersecting rows and columns for displacement along the rows and columns upon actuation of individual ones of the keys, the keys being arranged in positions corresponding to the intersections of the rows and columns of displaceable elements so that upon displacement of a key the elements in the respective row and the elements in the respective column intersecting in the intersection associated with the key are being displaced, there being switching means associated with the rows and columns of elements and actuated upon displacement of the elements in the respective rows and columns, the improvement comprising: an additional row of displaceable elements arranged alongside one said rows and arranged for limited displacement only of the elements of the additional row; and plural slide means, respectively associated with said columns and operatively coupled to the keys so that one slide means of the plurality is displaced upon depression of a key pertaining to the column with which the one slide means is associated, each slide means when displaced locking the elements of the additional row, so that the elements of the additional row inhibit displacement of the remaining slide means of the plurality thereby inhibiting depression of any key of the respective other columns.
 2. In a keyboard as in claim 1, wherein each slide means is constructed for operating, upon displacement, as stop for the keys of said column other than the one that has been depressed.
 3. In a keyboard as in claim 1, wherein each key is provided with means for selective engagement with the respective slide means when undisplaced, for displacement of the slide means upon further depressing of the key, the key remaining in engagement with the slide means and remaining depressed for as long as the slide means remains displaced, there being spring means to return the slide means upon release of the ley, whereupon the key is raised by engagement with the returning slide means.
 4. In a keyboard as in claim 3, and including timed locking means actuated upon depressing any of the keys and holding the respective displaced slide means in displaced position for a predetermined period of time, independently from the release of the key.
 5. In a keyboard as in claim 4, the timed locking means including a pawl locking any displaced slide means, and a timer for retracting the pawl for unlocking the slide means a predetermined period after depressing of the key.
 6. In a keyboard as in claim 1, including a first plurality of channels holding displaceable elements and a second plurality of channels holding displaceable elements and intersecting the channels of the first plurality, the elements in the channels of the first plurality defining the rows of elements, the elements in the channels of the second plurality defining the columns, the keys disposed above the channels, each key having a stem projecting down, next to, but not into the respective intersection to which the key pertains, the stem having first and second blades respectively placeable into the intersecting channels, the slide means of the plurality each including a slide with oblique cam slots, the stems of the key of the column to which the slide means pertains having pins insertable into the cam slots upon depression of a key and when the slide is not displaced.
 7. In a keyboard as in claim 1, wherein said slide means include a slide with a plurality of slots having oblique orientation to both, a direction of sliding displacement of the slide means and to directions of displacement of the keys on the respective column, each key on the column having a pin for entering a slot of the plurality upon depression of a key thereby sliding the slide in the said direction; and spring means for retracting the slide when a depressed key is released, whereby the respective slot guides the pin to return in up direction, the released key following that up return. 